bushes in a bad way
have recently moved house and our new place has three blackcurrant
bushes. They look in a bad way looks like lots of rust on
the leaves and not good leaf colour. What do we do and when should
we do it?
(Ribes nigra) are usually quite easy to grow, but do prefer
cooler and drier conditions. If you are living in a warmer, wetter
area, or if it has been wetter than usual (which it has), it is
likely that the blackcurrant bushes are suffering from fungal attack.
There are four likely culprits downy mildew (grey fluff),
powdery mildew (powdery deposits on the leaves), rust (rusty-orange
deposits on the leaves) or leafspot (yellowed spots on the leaves).
All four diseases would cause discolouration of the leaves. Other
possibilities are aphids or mites, or, worst of all, a virus.
What to do: If you have
a fungus and can work out which one it is, then choose an appropriate
fungicide and follow the instructions. Prune back and destroy old
shoots to promote healthy new growth. Make sure the bushes have
at least some sun, have good air movement through their stems and
fertilise well in the growing season with potash and nitrogen.
If you can see insects
or mites, then you will need an insecticide or miticide. Check carefully
for the instructions with regard to flowering (i.e. bees) and eating
the fruit after spraying.
If you have a virus you
may need to remove and destroy the old plants. There are new resistant
by Dr Dan Blanchon from Unitec's Diploma in Sustainable Horticulture and Bachelor
of Resource Management.
with permission from NZOOM Home and Garden content,
from the previous
The views expressed here are not necessarily those of the RNZIH